IP Multimedia Subsystem functional entity Figure 4 gives the IP Multimedia Subsystem functional structure constitute the functional entities and reference points, also shows the IP Multimedia Subsystem network and the parent entity in the network between the respondents how distributed.
Application Server (AS) AS provides IP Multimedia Subsystem Service Control. Application server directly with a service call session control function (S-CSCF) connection, or ISC reference point for the basic third-party applications, through an open services architecture (OSA) connectors to connect. ISC interface is based on Session Initiation Protocol, so the Session Initiation Protocol messages can be forwarded to this interface to the service call session control function, or reverse forwarding. Application Server users with home network server (HSS) Sh interface in the interaction to get the user identity information. Application server to support a variety of phone categories of services such as call transfer and the number of translations, and can support the current situation, session control and services like online billing.
Open the connection control function (BGCF)
BGCF received by the service call session control function or another to open connection to the session control function forwarding the request, and select a net to open soon in the PSTN network. It can select one of the other networks to connect local media control functions, or open the link with the level control. This in turn other network connection control function to select a capacity of networks to optimize the respondents to the public switched telephone network routing, it is hoped that operators and support.
call session control function (CSCTs) IP Multimedia Subsystem
CSCTs responsible for the session control. It is coordinated with other network elements to control the characteristics of the session, routing and resource allocation. IP Multimedia Subsystem structure in three different types of call session control function:
Road Service Call Session Control Function (S-CSCF)?? It is sending or receiving a session of the user home network device session key control points.
Road inquired about the call session control function (I-CSCF)?? It is from the other network to the user’s home network device where the contact point.
Road proxy call session control function (P-CSCF)?? It is from the user equipment to the IP Multimedia Subsystem point of contact.
home network users to the server (HSS)
HSS contains an IP Multimedia Subsystem registration database, which contain information relating to the registration. These information support network entity handling the call or session. It supports system-level IP Multimedia Subsystem confirmation and approval, and control IP Multimedia Subsystem user’s identity. It also save the current specified service call session control function.
Home network can contain one or more network users home server, their number depending on the number of users, equipment capacity and network organization.
media connection control functions (MGCF) Support for IP Multimedia Subsystem
MGCF and PSTN interconnection, also supports the session initiation protocol to the ISUP protocol conversion and control the load level transformation of the media connection.
media connector (MGW)
MGW connection control functions in the media under the control and support IP Multimedia Subsystem and the public switched telephone network interconnection. It terminates the circuit switched network carrying channels and packet-switched network media streaming, and complete media conversion functions such as code conversion.
Topic:cscf, functional architecture, functional entities, functional entity, ip multimedia subsystem, protocol messages, pstn network, public switched telephone network, session control, session initiation protocol